The present invention relates to pulverized solid fuel (powdered coal) delivery systems and, more particularly, to a fuel head assembly for use in a pulverized coal delivery system.
Solid fuel furnaces, such as those used in boilers and steam generators typically burn powdered (pulverized) coal that is entrained in flowing air. The pulverized coal/air is blown into the furnace through coal piping along with additional air to create a swirling fireball. The fireball heats water in pipes encircling the furnace to create steam.
Coal is pulverized in a pulverizer then blown through coal pipes, fuel heads, nozzle and nozzle tip into the furnace.
Since the pulverized coal/air is very abrasive, blowing the pulverized coal through these structures has the same effect as sandblasting. The pulverized coal wears through these elements, damaging them. Damages coal ducting can cause fires and explosions. Therefore, it is important to minimize damage done to the coal ductwork.
FIG. 1 depicts a cross-sectional, elevation view of a conventional solid fuel ductwork disposed within a fuel compartment 3 of a solid fuel-fired furnace, such as a boiler or steam generator. While only one fuel compartment 3 is shown, it will be appreciated that many fuel compartments 3 having solid fuel ductwork are typically employed.
The pulverized coal/air stream from a pulverizer is provided by a fuel pipe 10. Fuel pipe 10 is connected to a fuel head assembly 20. This conventional fuel head assembly 20 is simply elbow 21 that redirects the pulverized coal/airstream from a vertical direction to a horizontal direction. The outlet of the fuel head assembly 20 is connected to a nozzle assembly 50.
The nozzle assembly 50 includes a nozzle body 51 that increases the velocity of the coal/air stream and a nozzle tip 53, which protrudes into a combustion chamber of the furnace.
The nozzle tip 53 is designed to pivot to direct the pulverized coal/airstream to a specific location within the furnace.
The pulverized coal particles tend to aggregate at various paths as they pass through the ductwork based upon airflow pressures. These typically resemble ropes extending through the ductwork, and are referred to as ‘coal ropes’. The coal ropes amplify the erosion effect and also reduce the burning efficiency in the furnace. Therefore, it is desirable to break up coal ropes and evenly distribute the fuel particles within the airstream.
In order to reduce wear, and to reduce the formation of ‘coal ropes’, the design shown in FIGS. 2 and 3 was implemented.
FIG. 2 is a perspective view of a fuel head assembly 20, previously invented by the Inventors of the present application. The fuel head assembly 20 has an inlet port 27 and an outlet port 29. The fuel/airstream is received at the inlet port 27, passes through the fuel head assembly 20 and out of the outlet port 29. The outlet port 29 has an outlet port upper flange 35 and an outlet port lower flange 37 that are used to connect fuel head assembly 20 to nozzle assembly 50.
A removable cover 23 and lower casing 25 connect to each other to create an internal cavity being a curved tubular conduit fluidically coupling the inlet port 27 to the outlet port 29. Removable cover 23 includes a lifting lug 24, used to lift the removable cover 23.
In FIG. 3, replaceable, wear-resistant cover liner 41, and casing liner 43 are disposed within the internal cavity and shown in an exploded view. As shown here, bolts holding a cover upper flange 38 to a cover lower flange 39 are removed. The removable cover 23, cover liner 41 and casing liner 43 can then be removed in an upward direction. However, in some furnaces/boilers, there are structural members that are immediately above the fuel heads 20 making it difficult and time-consuming, or impossible to remove the removable cover 23, cover liner 41 and casing liner 43. Since power plants are shut down during maintenance, and replacement electricity must be purchased for every minute the power plant is off line, it is financially beneficial to complete the maintenance quickly.
Also, the design shown in FIGS. 2 and 3 has an output port flange that is in two pieces. When the removable cover 23 is removed, only the outlet port lower flange 37 is attached to and supporting the weight of the fuel head assembly 20 and the fuel pipes 10.
An inspection port 68 is provided to allow viewing or testing inside of fuel head assembly 20.
Therefore, currently, there is a need for a fuel head that can be easily serviced in spaces that are confined above the fuel heads, and is designed to provide additional support to the coal pipes when being serviced.